The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)
site maintained by the Florida
Cooperative Extension Service.

INTRODUCTION
There are at least three fundamental problems in the pro-
duction of celery in the Everglades. These are: (a) water con-
trol, (b) fertilization and (c) disease and insect control. Solu-
tions for the first two of these problems have been attained in
a considerable measure (1)2. On the other hand, the need for
disease and insect control measures will probably increase.

The diseases which affect celery in the Everglades may be
listed in their order of importance at present as: Early blight,
damping-off, late blight, deficiencies of minor elements, mosaic
root-knot and pink rot. Early blight is the most generally preva-
lent of all these diseases and it is impossible to grow marketable
celery in the Everglades if measures for the control of this di-
sease are not employed.

Experiments for the control of early blight were conducted
each year from 1931 to 1941. Several formulas and types of
bordeaux mixture and numerous other fungicides, both liquid
and dust, were tested.

"The experiments in 1931 and 1932 were conducted by the late H. H.
Wedworth, formerly Associate Plant Pathologist at the Everglades Ex-
periment Station.
"Italic figures in parentheses refer to literature cited in the back of
this bulletin.

4 Florida Agricultural Experiment Station

THE DISEASE
Early blight is a fungous disease caused by Cercospora apii
Fres. This fungus may be seen as a gray mold on blight-
ed celery leaves which have fallen on moist soil. This mold
consists of mycelium, conidiophores and spores of the fungus.
The microscopic hyaline spores are borne singly, or rarely in
chains, at the tips of brown conidiophores. There are from four
to 12 cells in a spore measuring 4.0 to 4.5 microns in diameter
by 55.0 to 100.0 microns in length. (4).
Early blight infections occur on leaves of all ages, and also
on the petioles. Pale yellow spots about a millimeter in diam-
eter develop on infected leaves in about a week after they have
been inoculated with the spores. These spots may enlarge to a
diameter of one or two centimeters, but most of them do not be-
come larger than a half centimeter. They are nearly circular in
outline unless two or more spots coalesce or they occur on the
leaf margin. The fully developed spots have a gray or grayish
brown center and a brown border. They extend through the
leaf to the opposite surface, and have a papery texture when
dry. Spores of the fungus are produced abundantly on the
conidiophores which arise over the surface of the lesion when
moisture is adequate. If the spots become numerous the leaf-
lets become chlorotic and wither and the leaf falls from the
plant.
Water-soaked brown lesions occur on the petioles when the
disease is severe. These spots may become several centimeters
long. They darken with age, and may bear a crop of conidio-
phores and spores.
Early blight is distinguished in the field from late blight
by the larger size of the early blight leaf spots and by the pres-
ence of numerous black pycnidia on the lesions produced by
the late blight fungus.
Infection occurs when spores germinate on the leaf and
send germ tubes through the stomata into the leaf tissue (4).
A high relative humidity of the air with some water on the leaf
are favorable to infection. The germination of the spores and
entrance of the fungus into the leaf can occur in as little as six
hours. Klotz (4) found that temperatures ranging from 72 to
84" F. were most favorable for spore germination. The infec-
tion becomes evident on the older leaves in five to eight days,

Control of Celery Early Blight 5

but on the young heart leaves 10 to 14 days are required. After
the fungus has become established in the plant further progress
of the disease is favored by high temperatures and a lack of
water in the plant. Blight is usually more severe on plants
growing in wet spots in the field, or following heavy rains that
have caused temporary flooding. Under these conditions the
roots are injured and the plants cannot absorb the water and
nutrients they need to resist the fungus.
In the Northern states the early blight fungus survives
through the winter on celery refuse. The survival through the
summer in Florida may be by the same means. It is also quite
probable that the fungus is introduced each season as mycelium
in the seed and in the chaff that accompanies most celery seed.
The disease appears first on the seedlings in the plant bed
and if not checked will kill the young plants or greatly retard
their growth. It is customary to apply bordeaux mixture, but
the control of the disease is never complete and always some
plants with blight lesions are set in the field. If conditions are
favorable for infection there may be a considerable development
of early blight on the yellowed leaves of plants soon after they
are set in the field. The new leaves which develop when the
plants recover from transplanting do not show much blight
unless conditions are extremely favorable for infection.
Early blight usually becomes severe when the plants are
half to two-thirds grown. At this time the disease occurs mostly
on the outer and older leaves, and if the growing leaves are pro-
tected with a fungicide the disease will not become serious.
Without such protection the plants become more and more
blighted so that by maturity there are lesions on all of the
leaves and the plants are chlorotic and stunted and the yield
and quality of the celery are reduced.

CONTROL OF EARLY BLIGHT
THE DEVELOPMENT OF COPPER FUNGICIDES
Klotz (4) has cited a number of references to the use of
ammoniacal copper carbonate, potassium sulfide and bor-
deaux mixture for the control of early blight of celery prior to
1900. In general these early experiments failed to develop ef-
ficient control measures.
Spraying celery with bordeaux mixture to control both the
early and late blights has been an accepted practice for more

6 Florida Agricultural Experiment Station

than 20 years, but experimentation has continued because of
the general dissatisfaction with the results from the use of this
material. Foster and Weber (2) found that 4-4-50 bordeaux
mixture, made with stone lime, gave best results at Sanford,
Florida, in 1924. Wilson and Newhall (8) recommended the
5-5-50 bordeaux formula (5-7%-50 if made with hydrated lime)
to Ohio growers in 1930. Nelson (7) advocated copper oxide-
sulphur dust mixtures and bordeaux sprays for the control of
celery blights in Michigan ih 1939.
During the last decade a number of studies of the composi-
tion of bordeaux mixture have been made. According to Mar-
tin (6) the reaction of a copper sulfate solution with a solu-
tion of calcium hydroxide produces a basic copper sulfate.
When the amount of calcium hydroxide added exceeds 0.75
molar equivalent the basic salt gradually decomposes and
an hydrated cupric oxid is formed. Hockenyos (3) found
that the color of the precipitate changes from greenish for the
tri-basic sulfate to greenish-blue for the tetra-basic sulfate
and to deeper shades of blue as the precipitate changes from
the higher basic sulfate to hydrated copper oxide in the more
alkaline mixtures. The usual bordeaux formulas contain a
large excess of lime, since only 0.82 pound of stone lime, or 1.08
pound of hydrated lime, is required for the maximum precipi-
tation of copper from a solution containing four pounds of
copper sulfate (3). Mader and Blodgett (5) in New York
sprayed potatoes with bordeaux mixtures of several formulas
and found the 5-1-50 superior to the 5-2/2-50, 5-5-50 and
5-7/2-50 formulas. Likewise the 5-2'-50 was superior to the
two mixtures with more lime. This effect was attributed to the
greater solubility of the copper precipitates in the low lime
mixtures.
TESTS AT THE EVERGLADES EXPERIMENT STATION
EQUIPMENT
The liquid fungicides were applied with power spraying
equipment. From 1931 to 1937 a Bean duplex spray pump was
used. This machine supplied 12 nozzles and was operated at
pressures of 175 to 250 pounds. A Friend motorpump was used
during the last four seasons. This also supplied 12 nozzles but
it was operated at pressures of 300 to 325 pounds. The rate of
application was approximately 100 gallons per acre. The sprays
were carried from the pump through a 300-foot hose to a four-

Control of Celery Early Blight 7

row spray boom. The boom at first was carried through the
field by two men, while two or three others handled the hose.
Later the boom was fitted with wheels to facilitate handling.
The nozzles were arranged with one above and one at each
side of each row. The position of the nozzles was adjusted as
the plants grew.
Dusts were applied with Progress and Root dust guns.
These were hand operated machines which delivered the dust
through a short tube to a pair of flared nozzles. However, in
the later experiments the nozzles were taken off and the dust
was delivered from the end of a straight tube.
METHODS
The fungicides were applied to celery growing on plots
replicated from four to eight times. The plots were distributed
in a regular order in each replication except for the last two
experiments in which a random arrangement was employed.
There has been a trend towards the use of larger plots and
more replications in the later experiments. The celery was set
in the field in December or early January.
The fungicides were applied with the above mentioned
equipment in a manner as near commercial practice as was
possible. All of the treatments were applied once a week, ex-
cept where the timing of the sprays was varied experimentally.
The first application was made about 20 days after the plants
were transplanted in the earlier experiments. In more recent
experiments only six to nine days intervened between trans-
planting and the first application of fungicides.
The data in Table 1 give for each of the 11 years the plot
size, number of replications, number of applications, fertilizer
practice, length of growing season, average daily temperature
and rainfall for the growing season, and average yield.
They have been examined for an explanation of the wide
range in yields during the 11 years. Prior to 1940 there was a
significant negative correlation (r = -.71) between yields and
precipitation. When the average precipitation was high the
yields tended to be low. This correlation does not exist for the
data as a whole because nitrogen was added to the fertilizer in
the last two years. Although the 1941 season was the wettest on
record, the yields were not depressed as much as would have
been expected without nitrogen in the fertilizer. Because of
the large seasonal variation the amount of fertilizer applied

8 Florida Agricultural Experiment Station

over the range of 500 to 1,600 pounds is not correlated with
yields. However, in the 1941 experiment when each plot was
split into two parts receiving 3-8-16 fertilizer at 1,000 and 1,500
pounds to the acre, respectively, there was a significant differ-
ence of 30 crates per acre in favor of the 1,500-pound rate of
fertilization.

TABLE 1.-PLOT SIZE, NUMBER OF REPLICATIONS, NUMBER OF FUNGICIDE APPLICA-
TIONS, KIND AND AMOUNT OF FERTILIZER APPLIED, NUMBER OF DAYS THE CROP
GREW, THE AVERAGE DAILY TEMPERATURE AND PRECIPITATION FOR THE CROP
PERIOD AND THE AVERAGE YIELD OF CELERY FOR EACH OF 11 YEARS.

EXPERIMENTAL RESULTS
The Data.-The records of the experiments consist of the
yield of marketable celery harvested from each plot and notes
on or numerical estimate of early blight control.
Yields were tabulated as field crates per acre. The field
crates contained 70 pounds of celery as cut and stripped in the
field, or 60 pounds when the leafy tops were cut off for packing
in 16-inch crates. The yield of packed crates generally was 25
to 35 percent lower than the field crate yield.
The scoring system which was used for seven years was
based on a scale of 10 points. Some latitude was allowed in
scoring the more severe degrees of blight damage. Experience
showed that two observers did not score plots in the same way,
but that their estimates of blight were relative throughout a
series of plots. The blight scale which was employed for scoring
the plots since 1935 is given below:

Control of Celery Early Blight 9

Score Amount of Early Blight
1 Trace of blight on lowest leaves.
2 A few lesions on all lower leaves.
3 Some blight on leaves at side of plant.
4-5 Numerous lesions on side leaves; some dead leaves.
6-8 Lower and side leaves severely blighted; some lesions
on top foliage.
9-10 Topmost foliage blighted; foliage becoming chlorotic;
lesions on the stalks.
The data from the experiments have been analyzed by the
analysis of variance method. A figure for the least significant
difference between any pair of average yields is appended to
each table showing the results of experimental treatments. Sim-
ilarly, the least significant difference between any pair of blight
scores is appended to the tables of data for the last seven years.
Components of Bordeaux Mixture.-Although the crystal-
line or "snow" form copper sulfate, which was used for eight
years, dissolved more readily than the older type of bluestone,
it had to be dissolved in a stock solution some time ahead of
mixing the bordeaux spray. A much finer grade of powdered
copper sulfate, which was used for the last three years, was
preferred because it was soluble instantly and could be added
to the water in the spray tank without the preparation of a
stock solution.
Stone or burned lime was used in the experiments until
1937. This material had to be carefully slaked with water and
TABLE 2.-THE AVERAGE YIELD OF CELERY AND AN ESTIMATE OF EARLY BLIGHT
CONTROL ON PLOTS OF THE DUSTING AND SPRAYING EXPERIMENT IN 1931.
Crates Estimate of
Treatment of Plots per Acre* Blight Control
4-5-50 Bordeaux spray + 1 qt. Penetrol 904 Good
4-5-50 Bordeaux spray 899 Good
2-5-50 Bordeaux spray + 2 lbs. nickel sul-
fate 818 Fair
2-5-50 Bordeaux spray + 2 lbs. zinc sulfate 814 Fair
20-80 Copper-lime dust 805 Fair
2-5-50 Bordeaux spray 2 lbs. manganese 763 Fair
sulfate
Sulphur dust 679 Poor
4-5-50 Zinc-lime spray 661 Poor
1:200 Sulphocide spray 430 Poor
None 213 Severe Blight

"*Minimum significant difference at 5 percent point is 172 crates.

10 Florida Agricultural Experiment Station

TABLE 3.-AVERAGE YIELD OF CELERY ON PLOTS OF THE DUSTING AND SPRAYING
EXPERIMENT IN 1932.*

"*Minimum significant differences at 5 percent point are 144 crates for
yields and 0.59 for scores.
(a) Treatments which showed a degree of blight control significantly
better than is common in the general culture of celery. A score of
2.5 is considered equivalent to the degree of control generally ob-
tained.
(b) Treatments which showed a degree of blight control significantly
poorer than is common in the general culture of celery.
TABLE 7.-AVERAGE YIELD OF CELERY AND ESTIMATE OF EARLY BLIGHT CONTROL ON
PLOTS OP THE DUSTING AND SPRAYING EXPERIMENT IN 1936.

"*Minimum significant differences at 5 percent point are 79 crates for
yields and 0.41 for scores.
(a) Blight control was not satisfactory with any of the treatments be-
cause of frequent showers which washed off part of the fungicide
deposit.

a stock solution prepared before it could be used for mixing a
bordeaux spray. It was considered superior to hydrated lime
when this series of experiments was started but the results of
the experiments did not warrant its use. Comparisons of bor-
deaux mixtures prepared with stone and hydrated limes were
made in 1935, 1936 and 1937. (Tables 6, 7 and 8.) There was
not a significant difference between the two types of bordeaux
mixture, although the hydrated lime bordeaux showed an av-
erage increase of 33 crates per acre over the stone lime bordeaux.
The hydrated lime was preferred because it did not need slak-
ing.
Comparisons between calcium and magnesium or "dolomit-
ic" limes were made in 1935 and 1936. (Tables 6 and 7.) The
production of celery was not significantly lower with the dolom-
itic lime bordeaux sprays in either year. Blight control was
rated slightly better with the calcium lime bordeaux mixtures.
Copper-Lime Ratios in Bordeaux Mixture.-Variations in the
ratio of copper sulfate to hydrated lime were tested in 1936, 1937,
1938 and 1939. (Tables 7, 8, 9 and 10.) In the first year the use
of 3, 4, and 5 pounds of hydrated lime to 5 pounds of copper

Control of Celery Early Blight 15

sulfate was tried. The production of celery and blight control
were identical when these mixtures were used. Comparisons of
bordeaux mixtures with 1.25, 2.50 and 5.00 pounds of hydrated
lime to five pounds of copper sulfate were made for three years.
In these tests the 5-2.5-50 bordeaux formula ranked above the
5-5-50 and 5-11/4-50 mixtures although the differences in yield
were not significant. (Tables 8, 9 and 10.) In 1939 blight con-
trol was rated significantly poorer for the 5-5-50 bordeaux.
There were indications of copper injury visible as yellow tips
on the leaves of plants sprayed with the 5-1.25-50 bordeaux.
Amount of Copper in Bordeaux Mixture.-In the 1931 ex-
periment (Table 2) half of the copper sulfate was omitted from
certain sprays to which the sulfates of manganese, zinc and
nickel were added. The production of celery was higher be-
cause of better early blight control on plots in which the spray
contained 4 pounds of copper sulfate rather than 2 pounds. It
is inferred that the reduction in disease control and yield was
due to insufficient copper rather than the presence of the
other metals in the spray. In subsequent experiments where
copper sulfate was used at the rate of 4 or 5 pounds to 50
gallons of spray there were no significant reductions due to
the addition of the manganese or zinc sulfates.
Comparisons of the 3-3-50, 4-4-50 and 5-5-50 bordeaux
sprays showed them to be equivalent in 1938 (Table 9), but
in 1939 (Table 10) the 4-4-50 formula was significantly better
than the 5-5-50 and 3-3-50 formulas. The 3-3-50 formula gave
significantly poorer blight control in 1939. In 1940 there were
no significant differences between the 5-2.5-50, 4-2-50 and
3-1.5-50 formulas (Table 11).
Frequency of Application of Fungicides.-Spraying with
5-5-50 bordeaux mixture every 10 days resulted in a significant
increase in yield over a plot sprayed similarly once a week in
1932 (Table 3). In 1933, however, there was a significant dif-
ference in favor of spraying with 5-5-50 bordeaux spray once
a week rather than every other week (Table 4). Dusting also
was more effective when done at weekly intervals.
Applications of two copper-lime dusts and a 5-5-50 bordeaux
spray at intervals of one, two and three weeks were compared
in 1934 (Table 5). Yields and blight control were best with
weekly applications, and decreased significantly when the fre-

16 Florida Agricultural Experiment Station

quency of application was reduced to every other week or every
third week.
It appeared sometimes that an application of spray or dust
could be omitted without serious consequences. This seemed
to be safe on young plants when the weather was cool and dry.
Because of this in 1939 the experiment included plots sprayed
with 5-2.5-50 bordeaux mixture every week, and other plots on
which certain applications were omitted when blight did not
seem to be threatening the crop. The consequence was that on
plots where the first three applications were omitted there was
a significant increase in blight and reduction in yield (Table 10).
When five applications were omitted during the season there
was a very serious increase in early blight and loss in yield.
Spreaders and Stickers Added to Bordeaux Mixture.-Va-
rious materials were tested which were supposed to improve
the distribution of the spray deposit on the celery leaf, or to
improve the adherence of the copper. The most extensive test
of these materials was in 1932 (Table 3) when additions of pene-
trol, kayso, dubay spreader No. 716, ferro-skim and sunoco
spreader to a 5-5-50 bordeaux gave slightly higher yields than
the same spray without these materials. The only significant
difference was in favor of sunoco spreader.
Additions of lethane, grasselli and orthex spreaders to bor-
deaux mixture in 1937, 1938 and 1940 showed insignificant re-
ductions in yield (Tables 8, 9 and 10). The control of early
blight did not appear to be affected.
Supplements to Bordeaux Mixture. Bordeaux sprays in
which half of the copper sulfate had been replaced by the sul-
fates of manganese, zinc or nickel were tested in 1931. The plots
sprayed with 2-5-50 bordeaux to which 2 pounds of manganese,
zinc or nickel sulfate had been added had more early blight and
yielded less than plots sprayed with a 4-5-50 bordeaux mixture
(Table 2). The lower yields from the plots sprayed with bordeaux
mixture with metal supplements are not significant. When the
amount of copper sulfate was not reduced in the later experi-
ments the additions of manganese and zinc sulfates to 5-5-50
bordeaux mixture had no effect. The 5-5-50 bordeaux spray
with 4 pounds of manganese sulfate was inferior to the 5-5-50
bordeaux in 1933 (Table 4), but equal to it in 1934 (Table 5).
Two-thirds of a pound of zinc sulfate added .to a 5-5-50 bordeaux
had no effect on yield in 1938 (Table 9). One pound of zinc

Control of Celery Early Blight 17

sulfate or 2 pounds of manganese sulfate had no significant ef-
fect when added to a 4-2-50 bordeaux mixture in 1941 (Table 12).
One pint of lime-sulfur solution was added to a 5-5-50 bor-
deaux spray in 1932 but the increased yield of 46 crates to the
acre was not significant (Table 3). Six pounds of wettable -sulfur
was added to a 5-5-50 bordeaux in 1938 and there was no sig-
nificant difference, as blight control and yields were very good
either with or without the sulfur (Table 9). In 1939 the 5-5-50
bordeaux spray with 6 pounds of sulfur gave much better con-
trol of blight than the 5-5-50 bordeaux (Table 10). Yields were
not affected significantly. With the 5-2.5-50 bordeaux formula
the addition of 6 pounds of wettable sulfur had no effect in this
experiment.
Two factory-mixed bordeaux-sulfur compounds were tested
in 1939. Wettable sulfur and bentonite clay had been added to
freshly prepared bordeaux mixture before it was dehydrated
and powdered. These materials were used for spraying in pro-
portions equivalent to 5-5-6-50 and 5-2.5-6-50 bordeaux-sulfur
sprays. The yield of celery on the plot sprayed with the 5-5-6-50
formula was not significantly different from that of the plot
sprayed with a field-mixed spray of the same formula. How-
ever with the 5-2.5-6-50 formula the field-mixed spray treat-
ment yields were superior to those of the factory-mixed pro-
duct (Table 10). This was believed to have been due to the ef-
fect of the bentonite which composed 18 Dercent of the mixture
in the second formula but only 12 percent in the first. Bentonite
was not added to the field-mixed bordeaux sulfur sprays, but
was necessary to keep the factory-mixed materials in suspension.
There was a heavier spray deposit on the plants sprayed with
the factory-mixed products and the control of early blight was
better with these products than with the field-mixed sprays.
In 1940 wettable sulfur was added to a 4-2-50 bordeaux spray
at 2, 4 and 5 pounds per 50 gallons. None of these mixtures was
significantly better than the other, nor were they different from
the 4-2-50 bordeaux spray without sulfur, as judged either by
production of celery or by blight control (Table 11). The 1941
experiment showed significantly better blight control on both
plots which received wettable sulfur at 2 pounds per 50 gallons
of spray. Yields were not affected significantly by the addition
of sulfur alone but when nutrients were added with the sulfur
there was a significant increase in production (Table 12).
Nitrate of soda and nitrate of potash were added to a 4-2-50

18 Florida Agricultural Experiment Station

bordeaux spray at 4 pounds per 50 gallons in the 1941 experiment.
Both materials tended to increase yields and interfere with blight
control. The increase in the blight score was significant in the
case of nitrate of soda. However, when both of these materials
and the sulfates of manganese and zinc were added to a 4-2-50
bordeaux with sulfur, there was a significant increase in yield
and a significant reduction in the blight score (Table 12).
Copper-Lime Dusts.-Mixtures of monohydrated copper sul-
fate and hydrated lime may be dusted on celery as a substitute
for bordeaux mixture. This method of controlling early blight
is more expensive than spraying and is not generally employed
except to obtain quick coverage if the regular spray schedule
has been delayed.
Plots were dusted with a 20-80 copper-lime mixture each year
from 1931 to 1938. During this period the bordeaux-sprayed plots
averaged 25 more crates of celery per acre than the dusted plots.
However, there were significant differences only in two years,
1931 and 1933 (Tables 2 and 4).
Dust mixtures containing more copper and less lime than in
the 20-80 mixture were tested in three years. In 1938 the plots
dusted with a 50-50 copper-lime mixture were the most produc-
tive plots in the experiment. Blight control was rated as average
(Table 9). In 1939 the 50-50 copper-lime dust plot was equal to
the 4-4-50 and 5-2.5-50 bordeaux spray plots in production, and
better than the 4-4-50 spray in blight control (Table 10). The
50-50 copper-lime dust caused injury to the celery in the 1940
experiment (Table 11). This season was cooler and considerably
wetter than the two seasons when the dust was not injurious. A
65-35 copper-lime dust was tried in 1938. It caused sufficient in-
jury to reduce the crop yield in that season (Table 9).
A mixture of copper-lime and sulfur (50-25-25) also was
tried in the 1940 experiment. The copper injury from this ma-
terial was more pronounced than with the 50-50 copper-lime
dust, and the production of celery was reduced (Table 11).
Copper Compounds as Bordeaux Substitutes.-Basic copper
sulfate is available in several forms (copotox, copofilm, tribasic).
"These products differ slightly in color due to the processes by
which they are manufactured. They are greenish to greenish-
blue powders having copper contents of 26 to 53 percent.
A basic copper sulfate (52 percent copper) was tested in the
1936 experiment. The yields of celery on the basic copper sul-

Control of Celery Early Blight 19

fate plots were equal to those with better treatments, but the
celery was of poor quality because the plants had more early
blight than with the bordeaux sprays (Table 7).
In 1937 the basic copper sulfate spray gave very inferior re-
sults as judged by blight control and the yield of sprayed plots
(Table 8). The quantity of material used in this experiment sup-
plied the same amount of copper as was contained in a 5-5-50 bor-
deaux mixture.
Four basic copper sulfates were tested in the 1938 experi-
ment. The yield of celery on plots sprayed with these materials
was lower than with 4-4-50 and 5-2.5-50 bordeaux sprays but
still within the range significantly equal to the best treatments
(Table 9). Blight control was poor with all of these compounds.
The addition of zinc sulfate as a sticker with basic copper sulfate
did not improve the yield of celery or the control of early blight.
A plot sprayed with a material then known only as copper com-
pound 25, but since marketed as a basic copper sulfate, ranked
second in yield of celery, but the material was inferior to bor-
deaux mixture for blight control.
A basic copper sulfate was tested with HPC sticker added
in 1939. The production of celery and the control of blight were
very inferior with this treatment (Table 10). In 1940 the copper
compound 25 which had been tested in 1938 was obtained under
a brand name. The control of 'blight was poorer but the produc-
tion of celery was as good as with bordeaux mixture when only
three pounds of the compound were used to the 50 gallons of
spray (Table 11). When four pounds were used the yield was
reduced.
Copper hydroxide (copper hydro 40) is a material similar to
basic copper sulfate. It has a copper content of 26 percent. The
results of tests with copper hydroxide showed that it was no
better than basic copper sulfate as a spray for celery. Blight con-
trol with copper hydroxide was inferior to that obtained with
bordeaux mixture in each of the four years (1936-1939) when it
was tested. The plots sprayed with this material generally were
less productive than bordeaux-sprayed plots (Tables 7, 8, 9
and 10).
Cuprous oxide (cuprocide) has been offered in several forms
since it was first introduced. In the first experiment with this
material the red copper oxide used for seed treatment was em-
ployed. Wettable forms have since been introduced by the
manufacturer. The yellow copper oxide which is now available

20 Florida Agricultural Experiment Station

is chemically identical with the red copper oxide. The differ-
ence in the color of the various cuorous oxides is due to the size
of the particles, since the color becomes lighter as the particle
size decreases. Because the particle size affects the number of
particles per pound of material and the distribution of the copper
on sprayed plants, it is held that the yellow copper oxide should
be more effective than the red oxide. The cuprous oxides have
metallic copper contents of 83 to 86 percent.
A mixture of red copper oxide, bentonite and lime was tested
in 1935. The proportions of the materials in this mixture were
1 part cuprous oxide, 1 part bentonite and 2 parts hydrated
lime. Celery sprayed with this material at 8 pounds per 50
gallons yielded as well as bordeaux-sprayed plants, but the con-
trol of early blight was poor (Table 6). In 1936 red copper oxide
with lethane spreader gave as high a yield and as good blight
control as the best bordeaux formula (Table 7). The copper con-
tent of the copper oxide spray was three times as great as that of
the bordeaux spray.
In 1937 when red copper oxide and bordeaux sprays of the
same copper content were compared the bordeaux sprays gave
much better control of early blight, but the production of celery
was not significantly different (Table 8).
In the 1938 experiment the older form of copper oxide used
with lethane spreader was compared with a new wettable form
of red copper oxide. The large difference in yield favoring the
new form of cuprous oxide was not significant. There was not
much difference in the degree of blight control. The new
wettable form of red copper oxide was as good as the better
bordeaux sprays (Table 9).
The wettable forms of red and yellow copper oxides were
compared in 1939. The yield difference between plots sprayed
with these materials was insignificant. There was a significant
difference between the blight scores which favored the yellow
copper spray, but neither material gave a degree of control
equal to that given by bordeaux mixture (Table 10).
Yellow copper oxide was applied to a single row of celery
with a knapsack sprayer in 1941. In this test where it was used
at the rate of 1.5 pounds per 100 gallons it was nearly equal to
a 4-2-50 bordeaux spray in the control of blight and the produc-
tion of celery. A bordeaux spray with the same copper content
probably would have been ineffective.
Basic copper chloride and copper oxychloride are similar

I

Control of Celery Early Blight 21

copper compounds recently introduced. The oxychloride (cup-
ro-K) is a pale green powder containing 24 percent copper ex-
pressed as metallic. Basic copper chloride (compound A) is a
blue powder containing 45 percent copper as metallic.
Copper oxychloride was inferior to bordeaux mixture as
judged by the blight scores in the 1936, 1938 and 1939 experiments
(Tables 7, 8 and 9). However, the plots sprayed with copper
oxychloride ranked third in yield and equal to the 4-4-50 bor-
deaux-sprayed plots in the 1938 experiment. In the 1939 experi-
ment the copper oxychloride spray gave very poor results.
The basic copper chloride spray (compound A) was tested in
1938, 1939 and 1940. In each season the control of blight with
this material was rated as about equal to that shown by bordeaux
mixture. The yield of celery on plots sprayed with basic cop-
per chloride was not significantly different from that of 4-4-50
bordeaux plots in any year (Tables 9, 10 and 11). It was better
than the 5-5-50 bordeaux spray in 1939. A basic copper chloride
and sulfur spray ranked first in yield of celery in 1939 and the
control of blight was equal to that with bordeaux mixture.
Copper ammonium silicate (coposil) sprays were tested in
1937, 1938 and 1939. This material contained only 20 percent
metallic copper. When used at the recommended rate (1.5-50)
in 1937, this material failed to control early blight and the yield
of celery was only slightly better than on plots that had not
been sprayed (Table 8). In 1938 this material was applied at a
rate (6.5-50) which supplied copper equivalent to a 5-5-50 bor-
deaux mixture. In this experiment the yield of celery was equal
to that with the 5-5-50 bordeaux spray, but the control of blight
was inferior to that with several bordeaux formulas (Table 9).
In the 1939 experiment the formula for this spray was again re-
duced (2-50) with the result that both yield and blight control
were inferior to that with 4-4-50 bordeaux mixture or 3-50 basic
copper chloride (Table 10).
Copper phosphate (41 percent copper) was used in a spray
with bentonite and lime in the 1938 experiment. Since 1 part of
bentonite and 2 parts of lime were used with the copper phos-
phate, the spray deposit was very heavy and the plants appeared
to have been injured by the surplus of lime on the leaves. The
yield of celery and the control of blight were very poor with this
material (Table 9).
An ammoniacal copper carbonate solution (super-copper)

22 Florida Agricultural Experiment Station

containing 15 percent copper as metallic was tested in 1937. Al-
though this material was used at the concentration (1:400) rec-
ommended by the manufacturer the yield of celery and blight
control were very inferior to those obtained with bordeaux and
cuprous oxide sprays (Table 8).
Ready-to-mix and prepared bordeaux sprays (duo-bordo
and fungi-bordo) were tested in 1933. These were not compared
with bordeaux mixture of an equal copper content, but were
somewhat inferior to a 5-5-50 bordeaux spray (Table 4). In
1934 and 1935 when the duo-bordo was compared with bordeaux
mixture having the same copper content there were no signifi-
cant differences in yield or blight control (Tables 5 and 6). The
duo-bordo consisted of two conveniently weighed packages of
easily soluble copper sulfate and hydrated lime which could be
used for mixing bordeaux in the field. Results with this material
were in line with those of the later experiments in which pow-
dered copper sulfate and hydrated lime were used for making
bordeaux mixture.
Sulfur Fungicides.-Sulphocide was used at the concentra-
tion of 1:200 as a spray treatment in the 1931 experiment. This
material contains sulfur in the form of polysulfides. It gave
poor control of the early blight and the yield of celery was much
less than with any other spray treatments (Table 2). Sulfur dust
also was tried in this experiment. The control of blight was
poor but the yield of celery was better than with the sulfocide
spray. The sulfur dust treatment was definitely inferior to the
20-80 copper-lime dust treatment and the 4-5-50 bordeaux spray
treatment. A 1:40 lime-sulfur solution was inferior to 20-80
copper-lime dust and 5-5-50 bordeaux spray in the 1932 experi-
ment (Table 3).
Wettable sulfur was used at the rate of 4 pounds to 50
gallons of water in the 1936 experiment. It failed to control
blight or to increase yield (Table 7). The favorable effects of the
addition of wettable sulfur to bordeaux mixture have been noted
previously.
Zinc Compounds as Bordeaux Substitutes.-The negative ef-
fect of the addition of zinc sulfate to bordeaux mixture has been
mentioned. A spray containing 4 pounds of zinc sulfate and five
pounds of lime to 50 gallons of water was tested in 1931. Blight
control was poor, but the yield of celery was increased consider-
ably (Table 2). It is probable that the zinc acted more as a
nutrient than as a fungicide. In 1935 a spray containing 2 pounds

Control of Celery Early Blight 23

of zinc oxide, 2 pounds of bentonite, and 4 pounds of hydrat-
ed lime to 50 gallons of water was tested. This spray failed to
control early blight and the yields were inferior to those on plots
sprayed with bordeaux mixture (Table 6).
Vapo-Dusting.-Dusting equipment is being developed which
is superior to the old equipment. A vapo-dusting machine
which applied copper dusts and oil simultaneously was available.
for field tests in 1941. This machine gave better distribution of
the dust and the adherence of the fungicides was better than
was obtained with the conventional type of duster. Cuprous
oxide dusts were applied to celery at the rate of 35 pounds of a
7 percent dust per acre per week. The control of early blight in
this field scale test was better than with bordeaux mixture ap-
plied more frequently. Comparative yields obtained by harvest-
ing check rows in each block showed a 90 percent gain for the
vapo-dusted plots (Table 13). The quality of the celery was
considerably better on the dusted plots.
DISCUSSION OF RESULTS
Comparisons between bordeaux mixture made from the
various forms of copper sulfate and lime seem to favor the use
of the powdered copper sulfate and calcium hydrate. These ma-
terials require no preliminary preparation and enable the grow-
er to mix his spray in the field. Their use is warranted because
of convenience as well as their demonstrated equality with or
superiority to other forms of copper and lime.
The 5-5-50 bordeaux mixture and the 20-80 copper-lime dust
leave a considerable surplus of lime on the plants. While this
does not seem to be a detriment in cool, wet seasons, it some-
times proves to be injurious in the warmer and drier months.
Some copper injury from the use of too little lime has been noted
with the 5-1.25-50 bordeaux mixture and the 65-35 copper-lime
dust whenever they have been tried. The 5-2.5-50 bordeaux has
never caused appreciable injury, nor has the 50-50 copper-lime
dust except in one cool and wet season.
There has been no evidence that more than 4 pounds of
copper sulfate is needed in 50 gallons of bordeaux mixture, but
the results have generally been unsatisfactory when only 2 or
3 pounds of copper sulfate have been used. When the spraying
equipment or methods are faulty the use of a higher concentra-
tion of copper will insure a heavier copper deposit. It would be
better to correct the faults in the equipment rather than to use
more material in the spray.

24 Florida Agricultural Experiment Station

Regularity is a virtue in spraying for early blight control.
The new growth should be covered with a well distributed de-
posit of spray every week. Unless the spray deposit is washed
off, more frequent application is not necessary. Too frequent
applications of bordeaux mixture are often harmful because the
heavy spray deposit stunts the plants. On the other hand, every
attempt except one to prolong the interval between applications
of bordeaux mixture resulted in poor blight control and lower
yields.
Spreaders and stickers did not improve bordeaux mixture in
these experiments except in one instance. The sunoco spreader
used in 1932 appeared to help. It is possible that the improved
wetting agents now available could be used to advantage. Because
of the hardness of the local water these wetting agents should
be used in excess of the recommended amount.
The sulfates of manganese and zinc and the nitrates of soda
and potash may be added to bordeaux mixture to take care of
certain nutritional deficiencies. These supplements do not affect
the value of the fungicide sufficiently to bar their use as the
occasion demands. Borax also has been added to bordeaux mix-
ture in a small scale test. The continued application of such a
spray may be harmful, but it may be used in part of the applica-
tions with benefit in the control of crack stem. All additions
should be made after the copper and lime solutions have been
mixed.
Wettable sulfur may be added to bordeaux mixture. There
is some reason to believe that the sulfur counteracts the effect
of the excess of lime in a 5-5-50 bordeaux mixture. In some of
the tests the control of early blight was considerably better where
the sulfur was added to bordeaux mixture. The bordeaux-sul-
fur spray deposit turns dark a few days after it is applied. This
probably indicates the formation of copper sulfides on the plant.
Copper compounds available as substitutes for bordeaux mix-
ture are somewhat unsatisfactory either because they do not
control blight as well as bordeaux mixture or they are too ex-
pensive. All of them have the advantage that the plants are not
coated with an injurious deposit of lime. The most effective of
these materials in these experiments were basic copper chloride,
red cuprous oxide, yellow cuprous oxide, and some brands of
basic copper sulfate.
Sulfur and zinc compounds did not prove satisfactory as

Control of Celery Early Blight 25

fungicides on celery. The fungicidal value of copper sprays may
be improved by the addition of sulfur, although it has no value
when used alone.
Vapo-dusting offers a considerable improvement in dusting
methods. The equipment needs further testing but this method
shows much promise of being superior to spraying because of
better distribution and adherence of the copper fungicides. The
red and yellow copper oxide dusts, when applied with vapo-
dusting equipment, were superior to bordeaux mixture applied
in the usual way.

RECOMMENDATIONS
Celery should be sprayed or dusted once a week on a regular
schedule, beginning 7 to 10 days after setting in the field. The
spray equipment should deliver 100 to 120 gallons of spray to the
acre per application and should operate at 300 pounds or higher
pressure in order to break up the spray and insure an even dis-
tribution of the deposit on the plants. If dusts are used 30 pounds
of a 20-80 copper-lime dust or 20 pounds of a 50-50 copper-lime
dust should be applied. These dusts must be applied on wet fol-
iage. Cuprous oxide dusts may be applied with vapo-dusting
equipment on dry foliage.
Bordeaux mixture made with powdered copper sulfate and
hydrated lime is an excellent fungicide for celery. There is no
advantage in using magnesium dolomiticc) lime rather than the
high grade calcium limes.
Bordeaux mixture can be prepared with a copper-lime ratio
of 2 to 1. The reduced lime formulas are better for use in the
warmer and drier seasons. If the winter months are cold and wet
the best bordeaux formula is a 4-4-50 mixture, but for the fall and
spring the 4-2-50 formula is recommended.
Wettable sulfur may be added to bordeaux mixture to in-
crease its fungicidal value and to counteract the excess of lime in
the high lime mixtures. Two pounds of wettable sulfur is suffic-
ient for mixing with 50 gallons of bordeaux spray.
Nutritional supplements may be added to bordeaux mixture
without seriously reducing its fungicidal value. All additions
should be made after the copper and lime solutions have been
mixed.
The insoluble copper fungicides, such as the red and yellow
cuprous oxides, basic copper chloride and some of the basic cop-

26 Florida Agricultural Experiment Station

per sulfates, may be substituted for bordeaux mixture. These
materials do not have the stunting effect of the high lime bor-
deaux sprays, but their fungicidal value has not proven equal to
the bordeaux-sulfur spray for celery in the Everglades. The very
good results with the copper oxides applied with vapo-dusting
equipment suggest that these materials would be more effective
as sprays if their distribution and adherence can be improved.

SUMMARY
Results of spraying and dusting experiments with celery
over a period of 11 years are reported in this bulletin. This period
has been marked by a transition from a 5-5-50 bordeaux mixture
prepared from difficultly soluble granular bluestone and stone
lime to 4-2-50 and 4-4-50 bordeaux mixtures prepared from easily
soluble powdered bluestone and hydrated lime. During the latter
part of this period many insoluble copper compounds have been
introduced as substitutes for bordeaux mixture.
The experiments show that better results are obtained when
the copper-lime ratio is reduced to 2:1. The addition of wettable
sulfur to bordeaux mixture has been found to reduce the damage
caused by high lime bordeaux formulas and to improve the con-
trol of celery early blight. Several nutrient materials may be
added to bordeaux mixture without seriously interfering with its
fungicidal action.
Most of the insoluble copper compounds have been found
inferior to the improved bordeaux mixture formulas. The
cuprous oxides and basic copper chloride are the only insoluble
copper compounds which can be approved at this time.
LITERATURE CITED
1. Beckenbach, J. R. A fertility program for celery production on
Everglades organic soils. Fla. Agr. Exp. Sta. Bul. 333. 1939.
2. Foster, A. C., and G. F. Weber. Celery diseases in Florida. Fla.
Agr. Exp. Sta. Bul. 173. 1924.
3. Hockenyos, G. L. Solubility of bordeaux mixture. Phytopath.
21 : 231-234. 1931.
4. Klotz, L. J. A study of the celery early blight fungus, Cercospora apii
Fres. Michigan Agr. Exp. Sta. Tech. Bul. 63. 1923.
5. Mader, E. 0., and F. M. Blodgett. Effects of modifications of the
potato-spray program. New York (Cornell) Agr. Exp. Sta. Bul. 621.
1935.
6. Martin, Hubert. Studies upon the copper fungicides. I. The inter-
action of copper sulfate with calcium hydroxide. Annals Appl. Biol.
19 : 98-120. 1932.
7. Nelson, Ray. Tests of new dust and liquid fungicides in 1938 for
the control of celery leaf blights. Michigan Agr. Exp. Sta. Quar.
Bul. 21 : 295-307. 1939.
8. Wilson, J. D., and A. G. Newhall. The control of celery blights. Ohio
Agr. Exp. Sta. Bul. 461. 1930.